Deep ultraviolet (DUV) lithography is currently available for use in the fabrication of semiconductor devices. DUV lithography utilizes deep UV light to expose photoresist. Photoresists amenable to such sensitization include acid-catalyzed photoresists. Acid-catalyzed photoresists are discussed in detail in U.S. Pat. No. 4,491,628, issued Jan. 1, 1985 to International Business Machines Corporation (the contents of which are hereby incorporated by reference). These photoresists include a photoinitiator which generates acid upon exposure to deep UV light.
The use of acid-catalyzed photoresists results in some problems that have not been encountered with previously-known resists (such as mid-UV resists, namely novolac-resin based photoresists). These problems are thought to occur due to the presence of contaminants at the resist/substrate interface which interfere with the sensitization of the resist material. The problems are manifested as profile distortion at the resist/substrate interface, taking the form of "footing" on positive resists and "undercutting" on negative resists. As a result, the ability to control patterning to critical dimensions using the resist is detrimentally affected. This limits the usefulness of acid-catalyzed photoresists, which are desirable for use with deep UV photolithography.
It is therefore desirable to provide a method for applying these acid-catalyzed photoresists to a substrate, which method is not subject to contaminant problems and patterning distortion.